[OPTICAL REVIEW Vol. 6, No. 2 (1999) 93-96]

Extraction of Quasi-Straightforward-Propagating Photons Through a Scattering Medium by Up-Conversion Method as a Coherent Light Detection Technique

Kenji WADA,1 Yoshihiro MISHINA,1 Shigenori FUJIWARA,1 Hiromichi HORINAKA,1 Yoshio CHO2 and Tokuo UMEDA3

1Department of Physics and Electronics, Faculty of Engineering, Osaka Prefecture University, Gakuen-cho, 1-1, Sakai, Osaka, 599-8531 Japan, 2Oyokoden Applied Photonics Lab Co., Ltd., 5301, Haga, Okayama, Okayama, 701-12 Japan, 3School of Allied Health Sciences, KITASATO University, 1-15-1, Kitasato, Sagamihara, Kanagawa, 228-8555 Japan

(Received October 6, 1998; Accepted December 1, 1998)

Aiming at the realization of optical CT (computed tomography), the extraction of quasi-straightforward-propagating photons from optical pulses transmitting through a standard scattering medium of Intralipid-10% aqueous solution has been demonstrated by an up-conversion method (second harmonic generation). We have found that this operates as a coherent light detection method rather than a time-gate one and extends the dynamic range where the Lambert-Beer's law holds to ~86 dB. We have also proposed improvements to obtain the largest possible dynamic range by such an up-conversion technique.

Key words : optical CT, scattering, quasi-straight-forward-propagating photons, up-conversion, coherent light detection